has the crack moved at all? Is there room to stop drill it.They do that on car windshields but I don't know if that will work here.

I thought about that too, but not sure if 1) it would affect the tank integrity and 2) if it has to be done on the outside, not sure if it can be reached.

It hasn't moved overnight, will fill the ato and see if that affects it. It holds approx 8 gls of water.

that is what we would call a run!if left it will keep expanding!

best is to cut a smaller piece of glass and silicone over it to preventing for expanding

Do you any bits around dave that I could come grab from you this week?

I agree with a couple suggestions
Short of replacing the back pane, you'll need to drill the crack at it's end to stop it travelling
Then silicone a square of glass over the inside of the hole

Whatever you do, looks like you're pulling your sump out ( again ) :sad:

Im going to try Dave's suggestion without drilling the crack, unless someone here knows how to. As the crack is on the outside, assume the silicone glass will go on the outside as well? I can't pull the sump out, everything will need to be done where it is. If the sump has to be removed, I'll shut the tank down altogether.

Maybe Dave means the added piece would help to stop the glass from bowing out and allowing the crack to spread more easily ?

Otherwise I see no benefit to it without drilling

Maybe he could explain it a bit more ?

If he doesn't explain here, I'll call the shop tomorrow and see what can be done.

I just felt it again and it starts right in the corner at the bottom. What the heck would cause this? When my skimmer crapped out, I was able to deal with it without moving the sump. It hasn't moved in a year and a half. And there's nothing behind the sump except wires.

Just perplexed....

If I were you I will replace it and add extra foam underneath. This way I can get a good sleep.